android - Mulitple Fragment Outputs in GLSL 300 es -

while writing unit tests simple ndk opengl es 3.0 demo, encountered issue in using multiple render targets. consider simple fragment shader 2 outputs, declared in c++11 string literal.

const static std::string multipleoutputsfragment = r"(#version 300 es     precision mediump float;     layout(location = 0) out vec3 out_color1;     layout(location = 1) out vec3 out_color2;     void main()     {         out_color1 = vec3(1.0, 0.0, 0.0);         out_color2 = vec3(0.0, 0.0, 1.0);     } )"; 

i have correctly setup fbo 2 color attachments (via glframebuffertexture2d) , glcheckframebufferstatus comes gl_framebuffer_complete. call gldrawbuffers(2, &attachments[0]), attachments vector of gl_color_attachmenti enums. afterwards, compile , link shader, without linking or compile errors (just used simple vertex passthrough irrevelant post).

is there reason why can fragment location out_color1 not out_color2, using following opengles function?

auto location = glgetfragdatalocation(m_programid, name.c_str());

the correct location returned out_color1 of 0, when providing "out_color2" glgetfragdatalocation, function returns -1.

i'm testing on physical device, galaxy s4, android 4.4.4 adreno 320, opengl es 3.0.

if call:

glreadbuffer(color_attachment_1); glreadpixels(*);  

can see data write fbo?